Production methods of stevia extract.

Home > News > blog3 2025-01-09 • 10 Minute Reading

1. Introduction

Stevia Extract, also known as sweetleaf extract, has gained significant popularity as a natural sweetener in recent years. It offers a sweet taste without the high calorie content associated with traditional sugars. The production process of Stevia Extract is a complex yet carefully regulated procedure to ensure the quality and safety of the final product. This article will delve into the detailed production methods of Stevia Extract.

2. Harvesting of Stevia Plants

2.1. Selecting the Right Time

The harvesting of stevia plants is a crucial first step in the production of Stevia Extract. It is essential to choose the appropriate time for harvesting. Stevia plants are typically harvested when they reach a certain level of maturity. This is usually determined by factors such as the plant's height, the development of its leaves, and the overall growth stage.
Generally, stevia plants are harvested when they are about 60 - 90 days old. At this stage, the plants have accumulated a sufficient amount of the sweet compounds in their leaves, which are the main source of the Stevia Extract.

2.2. Harvesting Techniques

When harvesting stevia plants, it is important to use proper techniques to avoid damaging the plants. Hand - harvesting is often preferred, especially for small - scale production. Workers carefully cut the stems of the plants close to the ground using sharp scissors or pruning shears.
In large - scale commercial production, mechanical harvesters may be used. However, these machines need to be carefully calibrated to ensure that they do not cause excessive damage to the plants or leave behind a large amount of unharvested material.

3. Washing of Harvested Stevia

3.1. Purpose of Washing

After harvesting, the stevia plants need to be thoroughly washed. The main purpose of washing is to remove dirt, dust, and other impurities that may be present on the surface of the plants. These impurities can affect the quality of the final Stevia Extract if not removed.
Washing also helps to remove any potential contaminants such as pesticides or fertilizers that may have been used during the growth of the plants. This is important for ensuring the safety of the Stevia Extract for human consumption.

3.2. Washing Methods

Stevia plants can be washed using clean water. In some cases, a mild detergent or sanitizer may be added to the water to enhance the cleaning effect. However, it is crucial to ensure that any detergent or sanitizer used is food - grade and does not leave any harmful residues on the plants.
The plants are usually soaked in the washing solution for a short period, followed by gentle agitation to dislodge the dirt and impurities. After that, they are rinsed thoroughly with clean water to remove any remaining detergent or sanitizer.

4. Drying of Stevia Plants

4.1. Importance of Drying

Drying is an essential step in the production of Stevia Extract. It helps to reduce the moisture content of the stevia plants, which is necessary for the subsequent steps such as grinding and extraction. High - moisture content can lead to spoilage, mold growth, and a decrease in the quality of the final extract.
Drying also helps to preserve the sweet compounds present in the stevia plants. By removing the moisture, the chemical reactions that could degrade these compounds are minimized.

4.2. Drying Methods

Natural Drying
- Natural drying involves spreading the washed stevia plants in a well - ventilated area, such as a drying yard or a large, airy room. The plants are spread out in a thin layer to ensure good air circulation. This method is relatively simple and cost - effective, especially for small - scale production.
- However, natural drying is highly dependent on environmental conditions such as temperature, humidity, and sunlight. In humid climates, natural drying may take a long time and may not be sufficient to reduce the moisture content to the desired level.
Mechanical Drying
- Mechanical drying is often used in large - scale production. There are various types of drying equipment available, such as tray dryers, tunnel dryers, and fluidized - bed dryers.
- Tray dryers are simple and commonly used. The stevia plants are placed on trays, and hot air is circulated through the trays to dry the plants. Tunnel dryers are more suitable for continuous drying operations, where the plants are moved through a tunnel - like chamber with a controlled flow of hot air. Fluidized - bed dryers are more advanced and can provide more uniform drying by suspending the plants in a stream of hot air.

5. Grinding of Dried Stevia

5.1. Purpose of Grinding

Once the stevia plants are dried, they need to be ground into a fine powder. Grinding increases the surface area of the stevia material, which is beneficial for the extraction process. A larger surface area allows for more efficient extraction of the sweet compounds from the stevia plants.
Grinding also helps to break down the plant cells, releasing the intracellular components that contain the sweet substances. This is important for obtaining a high - quality Stevia Extract.

5.2. Grinding Equipment

Various types of grinding equipment can be used for grinding dried stevia plants. One common type is the hammer mill. A hammer mill uses a set of rotating hammers to break the dried stevia into small particles. It can produce a relatively fine powder depending on the speed of rotation and the size of the hammers.
Another option is the ball mill. In a ball mill, the dried stevia is placed in a cylindrical chamber along with grinding balls. As the chamber rotates, the grinding balls collide with the stevia, gradually reducing it to a fine powder. Ball mills are often used for obtaining a very fine and uniform powder.

6. Extraction of Sweet Components

6.1. Selection of Extraction Solvents

The extraction of sweet components from the ground stevia powder is a critical step in the production of Stevia Extract. The choice of extraction solvent is very important. Commonly used solvents include ethanol and water.
Ethanol is a good solvent for extracting stevia sweeteners because it has a relatively high solubility for the sweet compounds. It can also help to remove some impurities during the extraction process. However, ethanol - based extracts may require additional processing to remove the ethanol if the final product is intended for use in food or beverage products where ethanol is not allowed.
Water is another popular solvent for Stevia Extraction. It is a natural, safe, and cost - effective solvent. Water - based extraction is often preferred for producing Stevia Extracts that are suitable for use in a wide range of food and beverage applications. However, water may not be as effective as ethanol in extracting some of the less soluble sweet compounds.

6.2. Extraction Process

The ground stevia powder is mixed with the selected extraction solvent in a suitable container. The ratio of stevia powder to solvent is carefully controlled to ensure optimal extraction efficiency. Generally, a higher ratio of solvent to powder may result in a more complete extraction, but it also requires more solvent and may lead to a more dilute extract.
The mixture is then stirred or agitated for a certain period. This helps to ensure that the solvent comes into good contact with all parts of the stevia powder, facilitating the extraction of the sweet components. The extraction time can range from a few hours to several days, depending on factors such as the type of solvent, the temperature, and the fineness of the stevia powder.

7. Filtration of the Extract

7.1. Purpose of Filtration

After the extraction process, the Stevia Extract needs to be filtered. Filtration is carried out to remove any remaining solid particles from the extract. These solid particles may include undissolved stevia powder, plant debris, or other impurities that were not removed during the previous steps.
Removing these solid particles is essential for obtaining a clear and pure Stevia Extract. A pure extract is not only more aesthetically pleasing but also more suitable for use in various applications, especially in the food and beverage industries where clarity and purity are highly valued.

7.2. Filtration Methods

There are several methods of filtration that can be used for Stevia Extract. One common method is gravity filtration. In gravity filtration, the Stevia Extract is poured through a filter medium, such as filter paper or a porous membrane, placed in a funnel. The solid particles are retained on the filter medium while the liquid extract passes through under the force of gravity.
Another method is vacuum filtration. Vacuum filtration uses a vacuum pump to create a pressure differential, which speeds up the filtration process. In vacuum filtration, the Stevia Extract is placed in a Buchner funnel with a filter medium, and the vacuum pump is used to draw the liquid through the filter, leaving the solid particles behind.

8. Concentration of the Filtrate

8.1. Purpose of Concentration

The filtrate obtained after filtration still contains a relatively large amount of solvent, which results in a relatively dilute Stevia Extract. Concentration is carried out to increase the concentration of the sweet compounds in the extract. A more concentrated Stevia Extract is more useful for various applications as it can provide a stronger sweetening effect with a smaller amount of the extract.
Concentration also helps to reduce the volume of the extract, which is beneficial for storage and transportation. A smaller volume of concentrated extract takes up less space and is more cost - effective to transport.

8.2. Concentration Methods

One common method of concentration is evaporation. Evaporation can be carried out using heat. The filtrate is heated in a suitable container, and the solvent is evaporated off as vapor. The heat can be applied using a variety of heat sources, such as a hot plate or a steam - heated jacketed vessel. However, care must be taken not to overheat the Stevia Extract during evaporation as high temperatures can cause degradation of the sweet compounds.
Another method is membrane concentration. Membrane concentration uses a semi - permeable membrane to separate the solvent from the sweet compounds. The filtrate is passed through the membrane under pressure, and the solvent molecules, which are smaller than the sweet compounds, pass through the membrane while the sweet compounds are retained, resulting in a more concentrated extract.

9. Purification and Final Processing

9.1. Purification

After concentration, the Stevia Extract may still contain some impurities or unwanted substances. Purification is carried out to further improve the quality of the extract. One common purification method is chromatography. Chromatography can be used to separate the sweet compounds from other substances based on their different chemical properties.
Another purification method is crystallization. Crystallization can be used to isolate the pure sweet compounds from the Stevia Extract. By carefully controlling the temperature and concentration conditions, the sweet compounds can be made to crystallize out of the solution, leaving behind the impurities.

9.2. Final Processing

Once the Stevia Extract has been purified, it may undergo final processing steps. These steps can include adjusting the pH of the extract to a suitable value for its intended application. For example, in some food and beverage products, a specific pH range may be required to ensure stability and taste compatibility.
The Stevia Extract may also be standardized to a certain level of sweetness. This is done by adjusting the concentration of the sweet compounds in the extract to meet the requirements of different applications. After final processing, the Stevia Extract is ready for use in various products as a natural sweetener.

FAQ:

What are the main raw materials for Stevia Extract production?

The main raw material for Stevia Extract production is the stevia plant. The fresh stevia plants are harvested and then go through a series of processing steps to produce the extract.

Why are ethanol or water used as extraction solvents?

Ethanol and water are commonly used as extraction solvents because they are effective in dissolving the sweet components present in the stevia powder. These solvents can selectively extract the desired sweet compounds from the ground stevia, leaving behind unwanted substances.

How is the drying of stevia plants carried out?

The drying of stevia plants can be carried out in two ways. One is through natural drying in suitable environments where the plants are left to dry under proper sunlight and air circulation. The other method is using drying equipment, which can control the drying conditions such as temperature and humidity more precisely to ensure efficient drying.

What is the significance of filtering the Stevia Extract?

Filtering the Stevia Extract is significant because it helps to remove any remaining solid particles. These solid particles may include undissolved plant matter or other impurities. By removing them, a purer Stevia Extract with better quality can be obtained.

How is the Stevia Extract concentrated?

The Stevia Extract is usually concentrated by removing the solvent. This can be achieved through methods such as evaporation under reduced pressure. By concentrating the filtrate, a Stevia Extract with a high concentration of sweet compounds can be obtained.